Mode C — Long-Term Backup (Insurance Policy) ⭐ Highly recommended for everyone

Best if: you want absolute peace of mind, plan to travel, or just don't trust yourself to remember.

This is the move I'd most strongly recommend you do right after Day 14 — before you've even baked your first loaf. Why? Because if your active starter ever dies, gets contaminated, or gets thrown out by a well-meaning roommate, you'd otherwise be back to Day 1 of the 14-day build. A backup eliminates that risk.

Method 1: Dehydrate (best long-term option)

Dried starter can sit in a sealed jar for years at room temperature, and revives in a single day.

When your starter is at peak (bubbly and active), spread a thin layer onto a piece of parchment paper. Aim for ~1–2 mm thick.
Let it air-dry in a warm, draft-free spot 24–48 hours until it's brittle and snaps cleanly. (You can also use a dehydrator on its lowest setting — never above 105°F (40°C), or you'll kill the yeast.)
Snap into shards or grind into powder in a food processor.
Store in an airtight jar in a cool, dry cupboard. Label with the date.

To revive: Add ~10 g of dried starter to 50 g warm water. Wait 30–60 minutes for it to rehydrate. Stir in 50 g flour. Let sit 12–24 hours at warm room temperature. Feed normally for 2–3 cycles and it'll be back to full strength.

Method 2: Freeze

Freezing works but is harder on the culture than drying.

Take ~50 g of peak starter, place in a small freezer-safe container or zip bag.
Freeze. Keeps 6+ months reliably, often longer.
To revive: Thaw at room temperature. Feed normally. Will likely need 3–5 feedings over 2–3 days to fully wake up.

Method 3: A Second Active Starter at a Friend's House

Genuinely the most foolproof backup — split off a portion of your starter and gift it to a friend who'll keep it going. If yours dies, you can grab some of theirs back.